Genetics of Swarming Motility in Salmonella enterica Serovar Typhimurium: Critical Role for Lipopolysaccharide
Genetics of Swarming Motility in Salmonella enterica Serovar Typhimurium: Critical Role for Lipopolysaccharide
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DOI：
10.1128/jb.182.22.6308-6321.2000
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发表时间：
2000-11
影响因子：
3.2
通讯作者：
A. Toguchi;Michael A. Siano;M. Burkart;R. Harshey
中科院分区：
文献类型：
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作者：
A. Toguchi;Michael A. Siano;M. Burkart;R. Harshey
摘要鼠伤寒沙门氏菌在适当浓度（0.5%-0.8%）的琼脂上可以分化为超鞭毛的群集细胞，从而使其在生长表面有效定植。鞭毛对这种运动形式是必不可少的。为了鉴定参与群集的基因，我们对鼠伤寒血清型进行了广泛的转座子诱变，筛选那些具有功能性鞭毛但不能群集的基因。这些突变体中的大多数是有缺陷的脂多糖（LPS）的合成，大量的是有缺陷的趋化性，和一些有缺陷的推定的双组分信号成分。虽然后两类在群集细胞分化中有缺陷，但代表性的LPS突变体没有，并且可以通过外部添加生物表面活性剂来拯救群集。waaG（LPS核心修饰）中的突变分泌了大量的粘液，并显示出早熟的群集表型。我们认为，O抗原提高了表面的“润湿性”所需的群体菌落扩张，LPS的核心可以发挥作用，粘液生成，多个双组分系统合作，以促进蜂群细胞分化。未能确定特定的群集信号，如氨基酸，pH值的变化，氧气，铁饥饿，粘度增加，鞭毛旋转，或autoinducers导致我们考虑一个模型，其中外部粘液本身既是信号和群集运动的环境。该模型解释了群集现象的细胞密度依赖性。
ABSTRACT Salmonella enterica serovar Typhimurium can differentiate into hyperflagellated swarmer cells on agar of an appropriate consistency (0.5 to 0.8%), allowing efficient colonization of the growth surface. Flagella are essential for this form of motility. In order to identify genes involved in swarming, we carried out extensive transposon mutagenesis of serovar Typhimurium, screening for those that had functional flagella yet were unable to swarm. A majority of these mutants were defective in lipopolysaccharide (LPS) synthesis, a large number were defective in chemotaxis, and some had defects in putative two-component signaling components. While the latter two classes were defective in swarmer cell differentiation, representative LPS mutants were not and could be rescued for swarming by external addition of a biosurfactant. A mutation in waaG(LPS core modification) secreted copious amounts of slime and showed a precocious swarming phenotype. We suggest that the O antigen improves surface “wettability” required for swarm colony expansion, that the LPS core could play a role in slime generation, and that multiple two-component systems cooperate to promote swarmer cell differentiation. The failure to identify specific swarming signals such as amino acids, pH changes, oxygen, iron starvation, increased viscosity, flagellar rotation, or autoinducers leads us to consider a model in which the external slime is itself both the signal and the milieu for swarming motility. The model explains the cell density dependence of the swarming phenomenon.